A spiroketal derivative having a certain structure has been known as being useful for preventing or treating diabetes (Patent Documents 1 and 2). For example, WO 2006/080421 (Patent Document 1) discloses a compound represented by the following formula (I), generic name of which is tofogliflozin (chemical name: 1,1-Anhydro-1-C-[5-(4-ethylphenyl)methyl-2-(hydroxymethyl)phenyl]-β-D-glucopyranose), and states that the compound has an excellent inhibitory activity against SGLT2.

Further, WO 2009/154276 (Patent Document 2) discloses a monohydrate crystal, a co-crystal with sodium acetate, and a co-crystal with potassium acetate of the compound represented by formula (I). The document further discloses that the monohydrate crystal (hereafter referred to as crystal form I) has peaks at diffraction angles (2θ) of about 3.5°, 6.9°, 10.4°, 13.8°, 16.0°, 17.2°, 18.4°, 20.8°, 21.4°, and 24.4° in X-ray powder diffraction pattern; the co-crystal with sodium acetate has peaks at diffraction angles (2θ) of about 4.9°, 8.7°, 9.3°, 11.9°, 12.9°, 14.7°, 16.0°, 17.1°, 17.7°, 19.6°, 21.6° and 22.0° in X-ray powder diffraction pattern; and the co-crystal with potassium acetate has peaks at diffraction angles (2θ) of about 5.0°, 10.0°, 10.4°, 12.4°, 14.5°, 15.1°, 19.0°, 20.1°, 21.4° and 25.2° in X-ray powder diffraction pattern.
Furthermore, WO 2012/115249 (Patent Document 3) discloses a monohydrate crystal of the compound represented by formula (I), and the monohydrate crystal (hereafter referred to as crystal form II) is characterized as having peaks at diffraction angles (2θ) of about 4.0°, 7.5°, 10.8°, 12.7°, 14.0°, 14.7°, 18.0°, 18.8°, 19.5°, and 22.7° in X-ray powder diffraction pattern. The document further discloses that an acetone-water solvate crystal (hereafter referred to as crystal form III) of the compound represented by formula (I) has peaks at diffraction angles (2θ) of about 11.0°, 12.3°, 19.2°, 20.2°, and 21.6° in X-ray powder diffraction pattern.
A pharmaceutical preparation containing a low-melting point drug significantly deteriorates in quality due to melting of the drug during storage at a high temperature, and this has been problematic. In powders or granules, melting of a drug causes coagulation. In tablets, melting of a drug causes problems, such as oozing of the drug, mottling, or changing in color, during storage, and adhesion of the tablet material to the tableting machine at tableting (sticking). To cope with such problems, JP 2006-160730 A (Patent Document 4) discloses producing granules from a mixture of an adsorbing carrier, such as calcium silicate, magnesium hydroxide-aluminium hydroxide co-precipitate, or synthetic hydrotalcite, with a low-melting point drug, as a means for handling problems, such as oozing of a low-melting point substance and coagulation of powders and granules, that arise during storage at a high temperature as well as tableting defects such as sticking. Further, JP H10-287561 A reports a solid preparation obtained by adsorbing ibuprofen having a low melting point on a porous excipient, such as calcium silicate or light silicic anhydride.
JP S56-145214 A (Patent Document 6) discloses obtaining tablets by adding silicates to a low-melting point substance as a stabilizer to increase the eutectic point and prevent melting of the substance, thereby to reduce variation in the content of the low-melting point substance from tablet to tablet and reduce changes in properties such as dissolution and hardness. JP S63-243034 A (Patent Document 7) discloses a solid preparation obtained by blending a low-melting point substance with calcium silicate that adsorbs the substance, thereby to reduce sticking. JP 2000-239185 A (Patent Document 8) discloses a pharmaceutical composition which has been granulated using light silicic anhydride to reduce, for example, sticking and the influence on stimulatory components (e.g., bitterness). JP 2005-104934 A (Patent Document 9) discloses a composition obtained by melting a low-melting point substance by initially blending it with calcium silicate, so as to prevent tablet-to-tablet variation in drug content at tabletting caused by melt of the low-melting point substance or to prevent prolonged disintegration time (to improve stability during storage).
From the production point of view, tablets are largely divided into following groups: compressed tablets, which are produced by compressing a medicine to a certain shape, and molded tablets, which are produced by moistening the ingredients of a medicine with a solvent and forming, or molding, the moistened mixture into a certain shape. The production of the compressed tablets is the highest of all dosage forms. Examples of typical production methods of the compressed tablets include direct powder compression (direct compression) and wet granulation compression. The direct compression is a process by which a medicinal agent and additives in powder form are mixed and the mixture is directly compressed into tablets. This process requires the fewest steps and is economical, whereas it may cause problems such as insufficient tablet hardness, powdery tablet surface, and lack of content uniformity from tablet to tablet or within each tablet. The wet granulation is a process in which a medicinal agent and additives are granulated by wet method and the granules are pressed into tablets. Although this process requires many steps, it is widely used due to many advantages it offers; for example, a medicinal agent is easy to be distributed uniformly in tablets, and covering the surface of a poorly water-soluble medicinal agent with a hydrophilic polymer (binder) can improve the dissolution and hardness of the tablets as well as prevent powders from appearing on the tablet surfaces (Non-Patent Document 1).